[ dhi vnunij.. .. 1 



j turning Hosin ond Bock J 

 \ Sound. Accumulation; y 



BOGUE BANKS. 



55 



Qe : Easterly Transport ol East 



End, Bogue Bonks 

 B w : Bar Bypassing lo the West 

 Be : Bar Bypassing to the Eost 



SHACKLEFORD BANKS 



I.I o t 

 0.26 Q E 



/ BOGUE BANKS |" 

 I (Volume Chonge from j 

 1 Shoreline History I .' 



' OCEAN BAR 



I (Volume Chonge from 



J 



-*-B E (SHACKLEFORD BANKS i 



, B * ' , ** \ (Volume Chonge from I **0.59Q E 



{ Bor Su " evsl jt^i^^L Ij" """ M ^J^ 0.2. Q E 



^ 



/ 



Loss Due to 

 Rising Sea Level 



Volume Removed 

 by Hopper Dredge 



Loss Due to 

 Rising Sea Level 



Figure 23. Schematized sediment budget analysis for Beaufort Inlet, North 

 Carolina (from Jarrett, 1976). 



Banks (Note that all longshore sand transport rates are expressed as a con- 

 stant times this transport rate; hence, the eastward longshore transport rate 

 at the west end of Bogue Banks is 1.1 Q E while the westward rate is 0.26 Q E , 

 etc.); By, the amount of sand bypassed to the west from the ocean bar; and 

 B £ , the amount of sand bypassed to the east from the ocean bar. The follow- 

 ing three equations, one for each element, can be written expressing conserva- 

 tion of sand in the system (refer to Fig. 23) 



1.1 Q E - Q E - 0.26 Q E + By + 5 - 32 = -153 (Bogue Banks) 



0.21 Q E + Bg - 0.34 Q E - 0.59 Q E - 33 = -245 (Shackleford Banks) 



Q E + 0.34 Q £ - By - B £ - 192 - 629 = -309 (Beaufort Inlet) 



where the quantities in the equations are in thousands of cubic yards per 

 year. Solving these simultaneous equations, the three unknowns are (in cubic 

 yards per year) 



Q E = 378,000 



By - -66,000 



B £ = 60,000 



The minus sign for By indicates that transport is in the opposite direction 

 from that assumed in Figure 23. 



The resulting sediment budget is the long-term average disposition of 

 sediments in the region. Sediment disposition in any given year may differ 

 from the results of the preceding analysis because of variations in wave 

 conditions, the occurrence of unusual storms, etc. Consequently, sediment 

 budgets for other time intervals should be constructed, data permitting. 

 Details of the variation in the sediment budget for Beaufort Inlet are 

 provided in Jarrett (1976). 



43 



